The foregoing application is to an invention communicated to the inventors of this application, after which this invention is made.
Thermal printing of the kind involved is in the nature of non-impact typewriting. Printing is by flow of melted material from a transfer medium which appears similar to a one-use typewriter ribbon. A lower lamination of the ribbon is heated, and printing is achieved by transferring ink from the ribbon to paper by means of local heating.
The foregoing application discloses an invention in which the correction ribbon is actually the marking ribbon. The outer material is colored for visibility of printing and melts at one temperature to thereby flow to a paper or other surface with which it is in contact. That same material is selected to become tacky at a temperature level between the printing temperature and room temperature. In practice the printer is backed over the erroneous character, the intermediate heat is applied, and the heated area is allowed to cool so that the bond sets before the ribbon is moved away from the printing plane.
As communicated to the inventors of this application, the ribbon feed during correction was beneficially changed from that during printing by the manual introduction of slack in the ribbon. The slack was introduced in the side near the ribbon supply. Although not apparent, during printing the slack portion would tend to stay on the paper, rather than being rolled toward the take-up spool immediately. This inherently introduced a delay which allowed the area heated during lift-off correction to cool before the ribbon was moved away from the printing plane.